Gratuity if company changes its name without intimation

Hi there
I worked with my previous organization for more than 12 years. I joined the company and after 4 years company changed its name and continued without any other updates. It doesn't have any PF or gratuity norms and thus I have not received my gratuity amount while FnF.
Now if I request for gratuity, will I be eligible for 12 years or 8 years gratuity?
Please suggest and how to write to company to pay me gratuity.
Thanks and regards.

Change if name does not absolvecompany from legal liabilities
Approach labor commissioner of the area for help if there is problem to get gratuity

Thank you for the response Mr Nathrao. This is really helpful.
When I left the company, they asked me to sign a paper where it was mentioned that I cannot work for 5 years in similar company and with same clients. With experience of more than a decade in same domain, for me, it is practically not possible to do so. They did not get it signed on stamped paper but it was a plain paper.
Now, when I have requested them for the gratuity, they specified that there is a conflict in trust and thus, they are going to seek legal advice.
How is it going to affect?

The terms on plain papers are unjust.
You have freedom to work anywhere in any capacity but only cannot poach candidates/clients from old company using your special knowledge of the client etc.
Action of withholding gratuity is not in order.Send them a proper letter duly verified by a lawyer and ask them to release gratuity legally due to you with interest and if they fail approach Labour Commissioner of area with your problem.

Thank you. This is really helpful and relieving. Will do as you suggested.

Do give feedback as to what happened finally.